Thermal infrared detector

ABSTRACT

An infrared detector comprising an infrared detector element for generating an electrical signal, a support for the infrared detector element, and a circuit board for receiving the electrical signal from the infrared detector element. The support is formed integrally with the circuit board. The support comprises a matrix of composite material essentially consisting of one of thermosetting resins and thermoplastic resins having a thermal deformation temperature of at least 100° C. and a tensile elastic modulus of at least 100 kgf/mm 2 , and of carbon fibers contained in the range of 10 to 40% by weight and dispersed in the matrix. The circuit board is formed with a through-hole having an inner surface processed so as to be electrically conductive.

FIELD OF THE INVENTION

This invention relates to a thermal infrared detector that is used indevices such as a radiation thermometer which measures temperaturewithout contact, or in trespass alarms that use infrared rays radiatedfrom a human body to warn of human presence.

DESCRIPTION OF THE PRIOR ART

Generally, infrared detectors are classified into two types, quantum andthermal. Quantum infrared detectors use the fact that a electric chargeis generated directly by infrared irradiation due to thephoto-electromotive effect and photo-conductive effect of the infrareddetection element, and thermal infrared detectors use the change inpolarization (pyroelectric-type detector), the change in resistance(bolometer) or generation of electromotive force (thermopile) that iscaused by the change in temperature of the infrared detection elementthat rises as infrared rays are absorbed. Moreover, thermal infrareddetectors must effectively convert incident infrared rays into heat, anda large temperature change of the element is necessary.

FIG. 8 shows the change of heat that is brought about by the infraredrays that are incident on the infrared detection element comprising aninfrared detector element 1, a circuit board 4 and a support 20 betweenthe infrared detector element 1 and the circuit board 4.

A part of the infrared rays that are incident on the infrared detectorelement 1 are reflected by the surface. The remaining part is eitherabsorbed by the element 1 or passes through the element and exits to theoutside. Of these infrared rays, those that can be effectively convertedto heat and that contribute to the large change of temperature of theelement 1 are the infrared rays that are absorbed by the element 1.

Moreover, the thermal energy of the infrared rays that are absorbed bythe aforementioned infrared detector element 1 not only cause thetemperature of the element 1 to rise, but are also radiated from thesurface of the element 1 and are consumed by convection or by beingtransferred to the support 20 that holds the element 1.

Therefore, in order to obtain a high-precision thermal type infrareddetector, it is necessary to increase the absorption efficiency ofinfrared rays, and it is necessary to reduce the heat that is lost fromthe infrared detector due to radiation, convection or heat transfer tothe element support. Normally the largest of these three kinds of heatloss is the heat that is lost due to heat transfer to the support of theinfrared detector element. In the prior art, there have been foursystems known for preventing the heat lost due to this kind of heattransfer.

(1) FIG. 9 shows the first system. Here, metal wires, which are alsoused as the lead wires for fetching the generated electric signal, areused as the support 21 for the infrared detector element 1. In thismethod, the amount of heat lost due to the aforementioned heat transferis the smallest, however it is very weak under impact and it isdifficult to produce.

(2) FIG. 10 shows a second system. Here, in place of the metal wiresused in the first method, metal pins are used as the support 22 for theinfrared detector element 1. In this method, inner pins (0.5 mm dia.) ofa detector package such as the TO-5 are commonly used metal pins;however, the heat capacity of this pins is large so the heat lossbecomes large, and the reduction in sensitivity of the detector cannotbe ignored. Therefore, when this method is actually used it is necessaryto use an infrared detector element whose surface area is larger thanthat of the photo-receptor electrode, and the portion of thephoto-receptor electrode whose temperature rises due to the infraredrays must be kept separated from the metal pins which fetch the electricsignal. Therefore, the material cost of the infrared detector element 1is very high, and there is a high possibility of the element 1 beingdamaged.

(3) FIG. 11 shows a third system. Here, an insulating material such asceramic, glass or resin that is formed in a rectangular block shape isused as the support 23 for the infrared detector element 1. In thiscase, the signal from the infrared detector 1 is fetched by a thin, goldwire 3 that connects the element 1 to the circuit board 4, or byapplying a conductive adhesive to the circuit conductor on the circuitboard 4. This method is the most widely used because it makes a verydurable infrared detector and is very good for mass production. However,in the method of using a thin, gold wire 3, it is very difficult toautomate the connection process and there is a reduction in sensitivityof the detector due to the heat lost from the connection area. Moreover,in the method of applying a conductive adhesive, the heat capacity ofthe conduction adhesive used in the infrared detector element is large,and so sensitivity of the detector drops. By using a rectangular blockshaped metal material as the support 23 for the infrared detectorelement 1, the problem of connecting the infrared detector element 1with the circuit on the circuit board 4 no longer exists; however, theproblem of preventing heat loss in the infrared detector element 1becomes more difficult.

(4) FIG. 12 shows a fourth system. Here, there is no support for theinfrared detector element 1. The element 1 is placed on the top surfaceof the circuit board 4 in which an adiabatic space has been formed byforming a through hole or depression in it, and the element 1 isconnected directly to the circuit board 4. In this case as well, thesignal from the infrared detector element 1 is fetched in the same wayas described in (3) above. Also it is possible to print the conductor asa thick film on the circuit board 4 that comes in contact with theelement 1 and use it directly as the leads. This method, the same asmethod (3) above, makes a very durable infrared detector and is verygood for mass production and is very commonly used. However, a circuitfor processing the signal is arranged on the surface of the circuitboard 4, so that often it is not possible to use a large area for theopening of the adiabatic space resulting in that the adiabatic effect isnot sufficient.

SUMMARY OF THE INVENTION

An objective of this invention is to provide an infrared detector thatis durable and which is suitable for mass production as in method (3)above.

Another objective of this invention is to provide an infrared detectorwhere it is not necessary to connect the infrared detector element withthe circuit board and it is possible to reduce as much as possible theheat lost to the support of the infrared detector element, thus beingable to do away with the problem of connecting the infrared detectorelement with the circuit board, and with the problem of heat loss in theinfrared detector.

Another objective of the present invention is to provide an infrareddetector that is advantageous over an infrared detector that comprisesan infrared detector element, a support for the infrared detectorelement, and a circuit board for receiving the electrical signalgenerated by the infrared detector element (called the prior infrareddetector below), in that the support is made of a composite materialthat uses a thermosetting resin or thermoplastic resin as the matrixdispersed with carbon fibers at 10 to 40% by weight and whose thermaldeformation temperature is 100° C. or greater and whose tensile elasticmodulus is 100 kgf/mm² or greater.

Another objective of the present invention is to provide an infrareddetector that is advantageous over the prior infrared detector in thatthe support is made of a composite material that uses a thermosettingresin or thermoplastic resin as the matrix dispersed with carbon fibersat 10 to 40% of weight and whose thermal deformation temperature is 100°C. or greater and whose tensile elastic modulus is 100 kgf/mm² orgreater, and where the inner surface of the through hole in the circuitboard is processed so that it is electrically conductive, and where thesupport and the circuit board are integrally formed.

Moreover, another objective of the present invention is to provide aninfrared detector that is advantageous over the prior infrared detectorin that the support is made of a composite material that uses athermosetting resin or thermoplastic resin as the matrix dispersed withmetallic fibers at 5 to 20% by weight and whose thermal deformationtemperature is 100° C. or greater and whose tensile elastic modulus is100 kgf/mm² or greater.

Furthermore, another objective of the present invention is to provide aninfrared detector that is advantageous over the prior infrared detectorin that the support and the circuit board are connected with conductiveadhesive, and where the support is made of a ceramic, thermosettingresin or thermoplastic resin whose (1) thermal deformation temperatureis 100° C. or greater, (2) tensile elastic modulus is 100 kgf/mm² orgreater and (3) thermal conductivity is 2 W·m⁻¹ ·K⁻¹ or less, and whosesurface is coated with a metallic film that is 0.1 to 1 μm thick.

Still, another objective of the present invention is to provide aninfrared detector that is advantageous over the prior infrared detectorin that the support is made of a ceramic, thermosetting resin orthermoplastic resin whose (1) thermal deformation temperature is 100° C.or greater, (2) tensile elastic modulus is 100 kgf/mm² or greater and(3) thermal conductivity is 2 W·m⁻¹ ·K or less, and whose surface iscoated with a metallic film that is 1 to 10 μm thick.

The objectives, features and advantages of the present invention willbecome obvious from the following detailed description of the presentinvention taken in part, with the drawings forming an integral partthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a partly cross sectional, front elevational view of theinfrared detector of a first embodiment of the first and thirdinvention;

FIG. 2 is a top plan view of the infrared detector element of theinfrared detector of the first embodiment of this invention;

FIG. 3 is a drawing showing the equivalent circuit that is formed on thecircuit board of the infrared detector of the first embodiment of thisinvention;

FIG. 4 is a cross-sectional view of the infrared detector of the firstembodiment of the second invention;

FIG. 5 is a partial cross-sectional drawing of the large circuit boardof the infrared detector of the first embodiment of the secondinvention;

FIG. 6 is a partial cross-sectional view of the mold cavity that is usedfor manufacturing the integral body infrared detector of the firstembodiment of the second invention;

FIG. 7 is a cross-sectional view of the infrared detector of the firstembodiment of the fourth invention;

FIG. 8 is a cross-sectional view that explains the transition of heatbrought by infrared rays that are incident on the infrared detectorelement of a prior type thermal infrared detector;

FIG. 9 is a cross-sectional view showing a first system used for a priorthermal infrared detector;

FIG. 10 is a cross-sectional view showing a second system used for aprior thermal infrared detector;

FIG. 11 is a cross-sectional view showing a third system used for aprior thermal infrared detector;

FIG. 12 is a cross-sectional view showing a fourth system used for aprior thermal infrared detector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with a first feature of the present invention, there isprovided an infrared detector where the support is made of a compositematerial whose matrix is a thermosetting resin or thermoplastic resinthat has a thermal deformation temperature of 100° C. or greater and atensile elastic modulus of 100 kgf/mm² or greater. Here, the thermaldeformation temperature is the temperature measured according to the JISstandards K 7206.

As the thermosetting resin, phenol resin, amino (urea) resin, melamineresin, unsaturated polyester, epoxy resin, etc., can be used, and as thethermoplastic resin, polypropylene, polystyrene, polyvinylchloride,polyacetal, polyamide (nylon), polycarbonate, polyphenylene ethyl,polyethylene terephthalate, polyarylate, polybutylene terephthalate,polysulfone, polyethersulfone, polyimide, polyamidimide, polyphenylenesulfide, polyoxybenzoyl, polyether etherketone (PEE-K), polyetherimide,liquid crystal polyester, polyphenylene oxide resin, etc. can be used.

The support made of a resin whose thermal deformation temperature isless than 100° C. will be unable to withstand the rise in temperatureduring the sensor assembly process for electrically connecting theinfrared detector element with the support. Also, the support made of aresin whose tensile elastic modulus is less than 100 kgf/mm², will beunable to solidly support the infrared detector element, and especiallyif the detector receives some kind of impact, a torsion force will beapplied to and could break the detector element.

In the first feature of the present invention, the support is made of acomposite material whose matrix is a thermosetting resin orthermoplastic resin, and it is dispersed with carbon fibers at 10 to 40%by weight. By dispersing the matrix with carbon fibers, the specificresistance of the composite material is 1000 ohms·cm; or less which issufficient for receiving the small signal current generated by theinfrared detector element, so that there is no need for a connectingwire between the infrared detector element and the circuit board.Moreover, the thermal conductivity can be kept to 2 W·m⁻¹ ·K⁻¹ or lesswhich is sufficient for extremely reducing the heat loss due to heattransfer to the support of the infrared detector element.

In order to reduce the specific resistance of the aforementionedcomposite material even more, and to increase the wetting of thecomposite material, it is possible to coat the surface of the carbonfibers with a metal plate such as nickel.

If the carbon fibers are dispersed at less than 10% by weight, then itis easy for the specific resistance of the composite material to exceed1000 ohms·cm; however, on the other hand, if the fibers are dispersed atmore than 40% by weight, then it is easy for the thermal conductivity ofthe material to exceed 2 W·m⁻¹ ·K⁻¹ and the moldability using anindustrial molding process such as injection molding, poured mold, orextrusion molding worsens. Moreover, in order to make the specificresistance of the composite material 1000 ohms·cm or less, and thethermal conductivity 2 W·m⁻¹ ·K⁻¹ or less, then the dispersion of thecarbon fibers in the material must be 10 to 50% by weight.

Next, in a second feature of the present invention, there is provide aninfrared detector where the support is made of composite material whosematrix is a thermosetting resin or thermoplastic resin that has athermal deformation temperature of 100° C. or greater, and a tensileelastic modulus of 100 kgf/mm² or greater.

If the support is made of a resin whose thermal deformation temperatureis less than 100° C., as was mentioned for the first invention above, itwill not be able to withstand the rise in temperature of the sensorassembly process, and it will not be possible to manufacture the supportand circuit board in an integral structure will be described below.

The carbon fibers used in the second invention and the amount that theyare dispersed are substantially the same as those described for thefirst invention.

When a filler such as metallic fibers and metallic flakes other than thecarbon fibers are dispersed in the matrix, the filler can get caught onthe surface of the circuit board or get tangled in the through hole inthe circuit board (1 mm dia. or less, usually about 0.5 mm) when formingthe support and circuit board in one piece, making it difficult for themolding materials to smoothly flow through the through hole and fill themold. In this regard, the carbon fibers, besides having good lubricationand elasticity, have a strength to be shorn when pressure is appliedeven if a pair of fibers are tangled; therefore, the molding materialscan smoothly flow through the through hole and fill up the mold with nogaps.

Furthermore, in the second feature, the support for the infrareddetector element and the circuit board are made in an integralstructure. They are made in an integral structure by introducing theaforementioned composite materials of the support through the throughhole formed in the circuit board and then allowing them to harden.Therefore, when molding them, in order to electrically connect thematerial of the support to the circuit board, the circuit board isformed with a through hole whose inside surface is processed with athick conductive film or plating is used. This molding process issimilar to the insert molding; however, it is different from the insertmolding in that the composite materials only make up part of the entiremolded part. Actually it is possible to use compression molding,transfer molding, injection molding, etc.

In order to improve the productivity of the circuit board, usuallyseveral tens of individual boards are made on a large single board andseparated from each other with a V-shaped cut, and then, after thesupport and circuit board are formed into an integral structure asdescribed above, the components are mounted onto the board. Then, theyare divided from each other. With respect to the material for thecircuit board, normally used epoxy resin with glass fibers can be used;however, when considering heat resistance, it is better if ceramic isused, and alumina is even better because of its good heat conductivity,and because it is good for the flow in molding of the compositematerial.

By making the support and circuit board into an integral structure, itis possible to manufacture the support and assemble it to the circuitboard all in one process.

In a third feature of the present invention instead of dispersing carbonfibers at 10 to 40% by weight in the matrix made of thermosetting resinor thermoplastic as in the first feature, metallic fibers are dispersedin the matrix at 5 to 20% by weight. The reason that the lower limit ofdispersed metallic fibers is 5%, and that the upper limit is 20% is thesame reason that the upper and lower limits of dispersion of carbonfibers are set in the first invention.

To prevent oxidation of the surface of the metallic fibers, and toincrease the wetting of the aforementioned matrix, the surface of themetallic fibers are coated with plating such as gold, tin, solder orindium.

In a fourth feature of the present invention, there is provide aninfrared detector where the support is made of ceramic, thermosettingresin or thermoplastic resin that has (1) thermal deformationtemperature of 100° C. or greater, (2) tensile elastic modulus of 100kgf/mm² or greater, and (3) thermal conductivity of 2 W·m⁻¹ ·K⁻¹ orless, and where a metallic coating is formed around the surface of thesupport.

The aforementioned characteristics, (1) and (2), are the same as thosedescribed for the first invention. Furthermore, for characteristic (3),if the thermal conductivity exceeds 2 W·m⁻¹ ·K⁻¹, the amount of heatloss due to heat transfer to the support of the infrared detectorelement increases.

If general ceramics are used for the support material, they willnormally satisfy characteristics (1) and (2). However, some ceramics,for example alumina, will not satisfy characteristic (3). Glasses arealso included in these ceramics.

Normally, the thermosetting resins or thermoplastic resins used for thesupport material will satisfy characteristic (3), and the thermosettingresins and thermoplastic resins mentioned for the first feature willsatisfy characteristics (1) and (2).

The aforementioned support is made of ceramic, thermosetting resin, orthermoplastic resin that meets the above characteristics and whosesurface is formed with a metallic coating. By forming the metalliccoating on the surface, the circuit board does not need a wire forconnecting it to the infrared detector element, and it is possible toadequately receive, through the metallic coating, the very small signalcurrent (for example, in the case of a pyroelectric-type infrareddetector element, the current is about 10⁻¹² A or less) generated by theinfrared detector element.

The metal used for this metallic coating is material that is normallyused in electronic circuits such as, copper, gold, silver, tin, nickelor solder, and is not specifically dictated.

In the fourth feature, the support for the infrared detector element andthe circuit board are connected by an electrically conductive adhesive,and the thickness of the aforementioned metallic coating must be 0.1 to1 μm. If the thickness is less than 0.1 μm, it does not function well asan electrically conductive coating, and if it is more than 1 μm, thethermal conductivity of the support material increases due to thecoating, and the sensitivity of the detector decreases, and its adhesionto the ceramic, thermosetting resin or thermoplastic resin underneaththe coating becomes poor.

To form the aforementioned metallic coating, the underlayer of ceramic,thermosetting resin or thermoplastic resin is roughed up as necessary inorder to improve the adhesion of the metallic coating, and then itshould be treated with chemical plating, or electrolytic platingseparately or in combination, as desired. Ceramic does not generallyneed roughing up, and it is good for forming the metallic coating on it.The mirror surface of plate glass also is sufficiently rough for formingthe metallic coating around if the surface is ground to the properdimensions and then cut. Also, for thermosetting resin and thermoplasticresin, it is possible to obtain the proper roughness if it is etchedusing a suitable chemical.

Finally, in a fifth feature of the present invention, instead ofconnecting the support in the fourth feature to the circuit board withelectrically conductive adhesive, it is connected by solder, and insteadof forming a 0.1 to 1 μm thick metallic coating as was done in thefourth invention, a thick metallic coating in the range of 1 to 10 μm isformed on the support. If this thickness is less than 1 μm, the factthat the coating is attacked by soldering cannot be ignored, and thesoldering conditions become poor. If the thickness exceeds 10 μm, thethermal conductivity of the support material increases and thesensitivity of the detector decreases.

Now, embodiments 1 thru 9 and comparative examples 1 thru 5 will begiven for the first invention.

EMBODIMENT 1

FIG. 1 shows the front elevational view of the assembled infrareddetector 30.

First, the support 24 for the infrared detector element 1 ismanufactured. In other words, the thermosetting resin, specificallyphenol resin (made by Sumitomo Bakelite Co., Ltd.), is used as thematrix of the composite material, and it is combined with 200 to 400 μmlong carbon fibers with an average diameter of 8 μm to make a compositematerial in which the carbon fibers are 30% by weight, and then thecomposite material is injected into a mold to form a molded piece of 1mm (width)×2 mm (length)×0.5 mm (thickness). The average thermalconductivity of this molded piece was measured using the laser flashmethod and found to be 0.4 W·m⁻¹ ·K⁻¹.

Next, as shown in the top plan view of FIG. 2, the infrared detectorelement 1 is formed with a porcelain plate 6 that is made of titanatelead zirconate in the dimensions of 3.0 mm (width)×4.2 mm (length)×0.1mm (thickness) and two electrodes 7 of 1.0 mm (width)×2.0 mm (height)are placed 1.0 mm apart in an H shape and attached using a vacuumevaporation method to the ceramic plate 6. The bottom surface of theseelectrodes has a little larger area than the corresponding top surface.The arrangement of these electrodes is called twin construction andtheir purpose is to detect human presence.

FIG. 3 shows the equivalent circuit formed by the circuit board. Theequivalent circuit of the circuit board 4 is made by soldering in ahigh-resistance resistor (5×10¹¹ ohms) and FET (2SK94), and then thecircuit board 4 is soldered to a TO-5 stem.

The aforementioned support 24, element 1, and circuit board 4 wereassembled as described below, and fifty infrared detectors 30 weremanufactured. In other words, the support 24 and element 1 wereconnected electrically and fastened together, and the support 24 andcircuit board 4 were connected electrically and fastened together usinga small amount of silver epoxy electrically conductive adhesive 8 (typeT-3030, manufactured by Sumitomo Metals and Mining Co.).

The sensitivity of the-obtained infrared detector sample 30 wasmeasured. The sample 30 was sealed by welding a cap, with a filter thatallows only 6.5 to 15 μm infrared rays to pass, to a stem in nitrogengas. Next, the infrared rays coming from a black-body furnace set at227° C. were passed through a chopper that was set at 1 Hz and weredirected onto the sample 30. When doing this, one of the twin electrodesinside the aforementioned sample was shielded.

The incident power at the location on the sample irradiated by theinfrared rays was measured using a power meter (model FTS-8110,manufactured by Ferrotex Co., Ltd.), and was found to be 2.9×10⁻⁴ W/cm².A storage oscilloscope (model VT-5730A, manufactured by MatsushitaElectronic Industries) was used to read the peak value of the responsewaveform of the sample output. The results showed that the averagesensitivity of the aforementioned samples 30 was 134 mVp-p.

EMBODIMENTS 2 AND 3

When manufacturing the support 24 for the infrared detector element 1,liquid-crystal polyester (product name VECTRA, manufactured by.Polyplastics Co., Ltd. (embodiment 2)), which is a thermoplastic resin,and polybutylene tereophthalate (product name VALOX, manufactured by GEPlastics Co. (embodiment 3)) which is a thermoplastic resin, were usedas the matrix for the composite material, and it was tested in the samemanner as was done for embodiment 1.

The results of embodiments 2 and 3 were as follows: the average specificresistance was 7.5 ohms·cm and 5.8 ohms·cm respectively, the averagethermal conductivity was 1.3 W·m⁻¹ ·K⁻¹ and 1.4 W·m⁻¹ ·K⁻¹ respectively,and the average sensitivity was 140 mVp-p and 135 mVp-p, respectively.

COMPARATIVE EXAMPLE 1

When manufacturing the support for the infrared detector element, thethermoplastic resin, ABS resin (manufactured by Asahi Chemical Co.), wasused as the matrix for the composite material, and it was produced andtested in the same manner as was done in embodiment 1.

The results showed that the average sensitivity of 136 mVp-p was good;however, during the heat treatment, there were some detectors whosesupport deformed during heat treatment, and thus use of this detector isnot reliable.

EMBODIMENTS 4 TO 6, COMPARATIVE EXAMPLES 2 AND 3

Carbon fibers of 200 to 400 μm length with an average diameter of 8 μmwere added so that the carbon fibers were 8 to 50% by weight in thecomposite material, and the composite material was injected into themold and tested in the same manner as was done in embodiment 2. Incomparative example 3, it was impossible to mold the resin, so the testwas canceled after molding. The obtained results are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________               Amount of carbon                                                                      Average Average thermal                                                                       Average                                               fibers added                                                                          specifie                                                                              conductivity                                                                          sensitivity                                           (% weight)                                                                            resistance (Ω cm)                                                               (Wm.sup.-1 K.sup.-1)                                                                  (mV.sub.p--p)                              __________________________________________________________________________    Comparative example 2                                                                     8      3.1 × 10.sup.3                                                                  0.9      86                                        Embodiment 4                                                                             12      9.4 × 10.sup.2                                                                  1.1     128                                        Embodiment 5                                                                             20      6.2 × 10.sup.                                                                   1.1     134                                        Embodiment 6                                                                             40      0.3     2.0     129                                        Comparative example 3                                                                    50      Molding --      --                                                            impossible                                                 Comparative example 4                                                                     8      1.0 × 10.sup.4                                                                  0.8     105                                        Embodiment 7                                                                             12      1.0 × 10.sup.3                                                                  1.0     125                                        Embodiment 8                                                                             20      4.2 × 10.sup.                                                                   1.3     130                                        Embodiment 9                                                                             40      0.1     1.9     127                                        Comparative example 5                                                                    50      Molding --      --                                                            impossible                                                 __________________________________________________________________________

EMBODIMENTS 7 TO 9, COMPARATIVE EXAMPLES 4 AND 5

Carbon fibers of 200 to 400 μm length with an average diameter of 8 μmwere added so that the carbon fibers were 8 to 50% by weight in thecomposite material, and the composite material was injected into themold and tested in the same manner as was done in embodiment 3. Incomparative example 5, it was impossible to mold the resin, so the testwas canceled after molding. The obtained results are shown in Table 1.

The detector of embodiments 1 thru 9 had superior average sensitivity;however, the average sensitivity of the detectors of comparativeexamples 2 and 4 was very poor.

Next, embodiments 10 thru 15 and comparative examples 6 thru 11 will bedescribed for the second invention.

FIG. 4 shows a cross-section of the assembled infrared detector 40.

First, as shown in the cross-section drawing in FIG. 5, in order thateach of the detectors can be divided up after being processed, a largeboard 10 (0.62 mm thick) with a V-cut 9 formed in it is used, from whichseventy two circuit boards 11 (9 rows×8 columns) made of alumina can beobtained. Three holes for each of the TO-5 stem pins to pass through,and two through holes 12 (0.6 mm diameter) through which the elementsupport material is filled for the integral molding, are formed in thecircuit board 11. The inside surfaces of the through holes 12 areprocessed so that they are electrically conductive by firing a thicksilver paste 13 on them. Moreover, the equivalent circuit shown in FIG.3 is formed for each of the circuit boards 11.

Next, the large board 10 is set in a prescribed location inside theinjection mold, and the support 25 for the infrared detector element 1and the large board 10 are integrally formed by injection molding. FIG.6 is a cross-sectional drawing showing the cavity of the metal mold 50.This metal mold 50 is different than a normal resin molding in that thetop mold 14 and the bottom mold 15 do not come in direct contact whenassembled together, but are separated by a gasket 16 made of asbestos orTeflon that acts as a buffer. If this gasket 16 is not used, becausedifferences in thickness and warps in the circuit board 11 occur, thecircuit boards 11 may break when placing the top mold 14 and bottom mold15 of the mold 50 together. In order to be able to use this gasket 16,the top mold 14 is ground off by 1.0 mm.

The material for the support 25 that was injected into this mold 50, wasa thermoplastic resin, liquid-crystal polyester (product name VECTRA,manufactured by Polyplastics Co., Ltd.), to which long carbon fibers of200 to 400 μm with an average diameter of 8 μm were added, so that theymade up 30% by weight of the mixture, and the dimensions of the support25 were 1 mm (width)×2 mm (length)×0.5 mm (thickness). The temperatureof the top mold 14 and the bottom mold 15 of the mold 50 duringinjection was 100° C.

The resistance between the surface of the support 25 and the circuitboard 11, which were made into an integral structure, was measured usinga voltmeter, and found to be 170 ohms. The molding conditions for thisintegrally molded structure were very good.

Furthermore, as was done in embodiment 1, fifty infrared detectors 50were manufactured from this integrally molded structure, and thesensitivity of these detector samples 50 was measured. As a result, itwas found that the average sensitivity of the samples 50 was 140 mVp-p.

EMBODIMENT 11 AND 12, COMPARATIVE EXAMPLES 6 AND 7

Resin, to which long carbon fibers of 200 to 400 μm with an averagediameter of 8 μm were added in the amounts showed in table 2, was usedas the material of the support that was injected into the mold, and thedetector samples were tested in the same manner as was done forembodiment 10. In comparative example 7, it was impossible to integrallymold the resin, so the test was canceled after molding. The obtainedresults are shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________               Matrix                                                                            Amount of carbon                                                                      Average                                                                            Integral                                                                            Average                                                Product                                                                           fibers added                                                                          resistance                                                                         Molding                                                                             sensitivity                                            resin                                                                             (% weight)                                                                            (Ω)                                                                          Conditions                                                                          (mV.sub.p--p)                               __________________________________________________________________________    Comparative example 6                                                                    Vectra                                                                             8      9000 Burrs  70                                                                     occurred                                          Embodiment 11                                                                            Vectra                                                                            15      2100 Good  135                                         Embodiment 12                                                                            Vectra                                                                            40       20  Good  135                                         Comparative example 7                                                                    Vectra                                                                            50      --   Molding                                                                             --                                                                      impossible                                        Comparative example 8                                                                    Valox                                                                              8      21000                                                                              Burrs  86                                                                     occurred                                          Embodiment 13                                                                            Valox                                                                             14      2300 Very Good                                                                           130                                         Embodiment 14                                                                            Valox                                                                             30       110 Very Good                                                                           138                                         Embodiment 15                                                                            Valox                                                                             40       15  Very Good                                                                           132                                         Comparative example 9                                                                    Valox                                                                             50      --   Molding e                                                                           --                                                                      impossible                                        __________________________________________________________________________

EMBODIMENTS 13 THRU 15, COMPARATIVE EXAMPLES 8 AND 9

A thermoplastic resin, polybutylene tereophthalate (product name VALOX,manufactured by GE Plastics Co. (comparative example 11)), to whichcarbon fibers of 200 to 400 μm length with an average diameter of 8 μmwere added in amounts shown in Table 2, was used as the material for thesupport that was injected into the mold, and it was tested in the samemanner as was done for embodiment 10. In comparative example 9, theresin could not be integrally molded, so the test was canceled aftermolding. The obtained results are shown in Table 2.

COMPARATIVE EXAMPLES 10 AND 11

Thermoplastic resin, liquid-crystal polyester (product name VECTRA,manufactured by Polyplastics Ltd, (comparative example 10)) andpolybutylene tereophthalate (product name VALOX, manufactured by GEPlastics Co. (comparative example 11)), to which copper fibers of 0.5 mmlength with a diameter of 30 μm were added so that they were 10% byweight in the composite material, was used as the composite material forthe support that was injected into the mold, and it was integrallymolded and tested in the same manner as was done in embodiment 10.

In all of the comparative examples, the composite material got pluggedin the gates of the mold, and it was impossible to obtain a good mold;therefore, the test was canceled.

Embodiments 16 thru 24 and comparative examples 12 and 13 will bedescribed for the third invention.

EMBODIMENT 16

Instead of carbon fibers, copper fibers of 5 to 6 mm length with anaverage diameter of 50 μm were added to the resin so that they were 15%by weight in the composite material, and this composite material wasinjected into the mold and tested in the same manner as was done inembodiment 2.

The results showed that the average specific resistance was 0.2 Ohms·cm,the average thermal conductivity was 1.3 W·m⁻¹ ·K⁻¹ and the averagesensitivity was 140 mVp-p.

EMBODIMENTS 17 THRU 19, COMPARATIVE EXAMPLES 12 AND 13

The resin to which copper fibers of 5 to 6 mm length with an averagediameter of 50 μm were added in the range of 3 to 25% by weight, andthis composite material was injected into the mold and tested in thesame manner as was done in embodiment 16. The obtained results are shownin Table 3.

                                      TABLE 3                                     __________________________________________________________________________                             Average                                                                            Average                                                    Metallic fibers                                                                             specific                                                                           thermal                                                                             Average                                                     Amount added                                                                         resistance                                                                         conductivity                                                                        sensitivity                                          Material                                                                             (% weight)                                                                           (Ω cm)                                                                       (Wm.sup.-1 K.sup.-1)                                                                (mV.sub.p--p)                             __________________________________________________________________________    Comparative example 12                                                                   Copper  3     200  0.9    86                                       Embodiment 17                                                                            Copper  5     10   1.1   129                                       Embodiment 18                                                                            Copper  8     0.7  1.1   134                                       Embodiment 19                                                                            Copper 20     0.06 1.8   124                                       Comparative example 13                                                                   Copper 25     0.001                                                                              2.1   119                                       Embodiment 20                                                                            Brass  15     0.3  1.3   139                                       Embodiment 21                                                                            Brass  20     0.08 1.9   121                                       Embodiment 22                                                                            Stainless Steel                                                                      15     0.5  1.2   126                                       Embodiment 23                                                                            Stainless Steel                                                                      20     0.02 1.8   123                                       Embodiment 24                                                                            Copper +                                                                             20     0.01 1.9   129                                                  Stainless Steel                                                    __________________________________________________________________________     NOTES:                                                                        1. Brass: Contains Zinc at 40% of weight                                      2. Stainless steel: SUS304                                                    3. Copper + stainless steel: Mixture ratio (by weight) 1:1               

EMBODIMENTS 20 THRU 24

Brass fibers, stainless steel fibers or copper+stainless steel fibersare used instead of copper fibers as the metallic fibers that were addedto the resin and injected into the mold and then tested in the samemanner as was done in embodiments 16 and 19. The obtained results areshown in Table 3.

Next, embodiments 25 thru 29, and comparative examples 14 thru 18, willbe described for the fourth invention.

EMBODIMENT 25

FIG. 7 shows a cross-sectional view of the assembled infrared detector60.

First, the support 26 for the infrared detector element 1 ismanufactured. A kitchen porcelain material having a thermal deformationtemperature of 100° C. or greater, a tensile elastic modulus of 100kgf/mm² or greater, and a thermal conductivity of 1.5 W·m⁻¹ ·K⁻¹ wasused as the support material, and this kitchen porcelain material wasmachined so that the porcelain material 17 had a rectangular block shapewith dimensions of 1 mm (width)×2 mm (length)×0.5 mm (thickness). Next,a nickel coating 18 of 1.1 μm thickness was formed around the surface ofthe porcelain material 17 using a chemical plating process. The chemicalplating was performed as follows. The aforementioned porcelain material17 was degreased for 30 minutes at 50° C. in a degreasing fluidcomprised of boric acid soda, phosphoric acid soda and an interfacialactive agent. It was then etched for 10 minutes at 65° C. in a mixturecomprising of chronic acid and sulphuric acid (400 g/l each), and thenrinsed. Furthermore, the porcelain material 17 was immersed in acatalyst comprising palladium chloride, stannous chloride andhydrochloric acid, after which palladium was precipitated on to theporcelain material 17 in sulphuric acid. Then it was processed for 15minutes at 40° C. in a chemical plating solution with a ph of 8 to 9,comprising nickel sulphate, hypophosphoric acid soda and ammoniumcitrate (at 30, 20 and 50 g/l respectively). The thickness of the formedcoating 18 was found by measuring the coating formed on a separate testsample of the porcelain material that was processed in the same way atthe same time as the aforementioned porcelain material 17.

As was done in the first embodiment, fifty infrared detectors 60 weremanufactured for samples, and the sensitivity and sensitivity balancewere measured for these detectors 60.

The results showed that the average sensitivity of the detectors 60 was122 mVp-p, and that the average sensitivity balance was 5%. Thesensitivity balance is the variation between V1 and V2, where V1 and V2are the sensitivity of the two electrodes, and is defined as(V1-V2)/(V1+V2)×100.

Moreover, a drop test was performed on the infrared detectors 60 whosesensitivity was measured. The infrared detectors 60 were dropped threetimes onto an oak board from a height of 75 cm, and then checked forabnormalities. As a result, no abnormalities were found on any of theinfrared detectors 60.

EMBODIMENTS 26 THRU 29

When manufacturing the support 26 for the infrared detector element 1,soda glass (thermal deformation temperature: 100° C. or greater, tensileelastic modulus: 100 kgf/mm² or greater, thermal conductivity: 0.6 W·m⁻¹·K⁻¹ (embodiments 26 and 27)), ABS resin (with a length of 200 to 400μm), glass fibers with an average diameter of 8 μm added by 20% byweight (thermal deformation temperature: 115° C., tensile elasticmodulus: 100 kgf/mm² or greater, thermal conductivity: 0.3 W·m⁻¹ ·K⁻¹(embodiment 28)), and polybutylene tereophthalate (thermal deformationtemperature: 100° C. or greater, tensile elastic modulus: 100 kgf/mm² orgreater, thermal conductivity: 0.2 W·m⁻¹ ·K⁻¹ (embodiment 29)) were usedas the support material, and a nickel coating was formed around it witha thickness as shown in Table 4 using chemical plating, and thusprepared and then tested in the same manner as was done for embodiment25 (however, in embodiments 28 and 29, the rectangular block shapedsupport was manufactured using injection molding). The thickness of thecoating was regulated by changing the temperature and processing time ofthe degreasing solution, etching solution, and chemical platingsolution. The obtained results are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                                         Coating  Average  Average                                            Support  thickness                                                                              sensitivity                                                                            sensitivity                                        material (μm)  (mV.sub.p--p)                                                                          balance (%)                                ______________________________________                                        Embodiment 26                                                                           Soda glass 0.15     126    3                                        Embodiment 27                                                                           Soda glass 0.9      127    6                                        Embodiment 28                                                                           ABS resin with                                                                           1.3      133    4                                                  glass fibers                                                        Embodiment 29                                                                           Polybutylene                                                                             0.9      136    4                                                  tereophthalate                                                      Comparative                                                                             Alumina    0.9      105    9                                        example 14                                                                    Comparative                                                                             Silicon rubber                                                                           0.8      130    7                                        example 15                                                                    Comparative                                                                             ABS resin  --       112    15                                       example 16                                                                    Comparative                                                                             Acrylic resin                                                                            --       129    19                                       example 17                                                                    Comparative                                                                             Polybutylene                                                                             --       117    12                                       example 18                                                                              tereophthalate                                                      ______________________________________                                    

The detectors of embodiments 26 thru 29 had very excellent averagesensitivity and sensitivity balance. Also, the results of the drop testfor the detectors of these embodiments were substantially the same asthose for embodiment 25.

COMPARATIVE EXAMPLES 14 AND 15

When manufacturing the support for the infrared detector element 1,alumina (purity: 96% by weight, thermal deformation temperature: 100° C.or greater, tensile elastic modulus: 100 kgf/mm² or greater, thermalconductivity: 20 W·m⁻¹ ·K⁻¹ (comparative example 14)) and siliconerubber (thermal deformation temperature: 100° C. or greater, tensileelastic modulus: less than 100 kgf/mm², thermal conductivity: 0.1 W·m⁻¹·K⁻¹ (comparative example 15)) were used as the material for thesupport, and a nickel coating was formed around it at thicknesses shownin Table 4 using a chemical plating process, and thus prepared and thentested in the same manner as was done for embodiment 25. The thicknesswas regulated by changing the temperature and processing time of thedegreasing solution, etching solution and electroless plating solution.The obtained results are shown in Table 4.

The average sensitivity balance of the detector of comparative example14 was good; however, the average sensitivity had greatly decreased.Also, the average sensitivity and average sensitivity balance of thedetector of comparative example 15 were good; however, during thechemical plating process, there were many poorly plated places where thecoating had peeled or the coating was insufficient, and the damage rateduring the drop test was 20%, which was very high.

COMPARATIVE EXAMPLES 16 THRU 18

Fifty of the infrared detectors shown in FIG. 11 were manufactured.

When manufacturing the support 23 for the infrared detector element 1,ABS resin (thermal deformation temperature: less than 100° C., thermalconductivity: 0.3 W·m⁻¹ ·K⁻¹ (comparative example 16)), acrylic resin(thermal deformation temperature: less than 100° C., thermalconductivity: 0.2 W·m⁻¹ ·K⁻¹ (comparative example 17)), and polybutylenetereophthalate (comparative example 18) were used as the supportmaterial, and no coating was formed around it using a chemical platingprocess. Also, when assembling the support 23 made of the aforementionedmaterial to the detector element 1 and circuit board 4, the detectorelement 1 and circuit board 4 were connected using a gold wire 3 of 30μm in diameter. This detector was then tested in the same manner as wasdone for embodiment 28.

The obtained results are shown in Table 4.

The average sensitivity of the detectors of comparative examples 16 thru18 was good or a little less than good; however, the average sensitivitybalance had increased, so that there were no parts that passed theexamination. Also, in comparative examples 16 and 17, when the support23 and element 1 were connected electrically and fastened together, andwhen the support 23 and circuit board 4 were connected electrically andfastened together, respectively, using a small amount of silver epoxyelectrically conductive adhesive 8 (type T-3030, manufactured bySumitomo Metals and Mining Co.), the detectors were deformed, resultingin assembly failures due to the lower thermal deformation temperature ofthe support material.

Finally, embodiments 30 thru 34, and comparative examples 19 thru 22will be described for the fifth invention.

EMBODIMENTS 30 THRU 32, COMPARATIVE EXAMPLES 19 THRU 24

Here, the support material was covered with nickel coating withthickness as shown in Table 5, using a chemical plating process orcombination of chemical and electrolytic plating processes; whenassembling the support, detector element and circuit board, solder wasused to electrically connect and fasten the support to the detectorelement, and to electrically connect and fasten the support to thecircuit board. The detector was thus prepared and then tested in thesame manner as was done for embodiment 26. When performing thesoldering, cream solder was applied to the circuit board, and then thesupport was placed on top of it and passed through a reflow furnace.

The results of the obtained samples are shown in Table 5. In comparativeexamples 19 thru 21, the soldering conditions were poor, and thereforethe tests were canceled after assembling the detector.

                  TABLE 5                                                         ______________________________________                                                Coating           Average  Average                                            thickness                                                                            Soldering  sensitivity                                                                            sensitivity                                        (μm)                                                                              condition  (mV.sub.p--p)                                                                          balance (%)                                ______________________________________                                        Comparative                                                                             0.08     Soldering  --     --                                       example 19         impossible                                                 Comparative                                                                             0.23     Soldering  --     --                                       example 20         impossible                                                 Comparative                                                                             0.55     Soldering  --     --                                       example 21         impossible                                                 Comparative                                                                             0.80     30% bad    125    5                                        example 22                                                                    Embodiment 30                                                                           1.5      95% good   129    6                                        Embodiment 31                                                                           4.0      100% good  128    6                                        Embodiment 32                                                                           7.9      100% good  128    3                                        Comparative                                                                             10.7     100% good  118    8                                        example 23                                                                    Comparative                                                                             15.1     100% good  113    5                                        example 24                                                                    ______________________________________                                    

As can be seen in Table 5, in embodiments 30 thru 32, the solderingcondition, sensitivity and sensitivity balance were all good. Incontrast to this, the soldering conditions in comparative examples 19thru 22 were extremely poor in plating; in comparative example 23, thesensitivity and sensitivity balance had decreased; in comparativeexample 24, the sensitivity had decreased.

Moreover, the drop test was performed for embodiments 30 thru 32, andthere were no detectors in which any abnormalities were found.

Lastly, an example of a prior detector will be described.

PRIOR EXAMPLE

Fifty infrared detectors as shown in FIG. 11 were manufactured.

When manufacturing the support 23 for the infrared detector element 1,ordinary plate glass (1 mm (width)×2 mm (length)×0.5 mm (thickness)) wasused as the material. Also, when assembling the support 23, made of theaforementioned material, with the detector element 1 and circuit board4, a wire 3 of 30 μm diameter was used to connect the detector element 1with the circuit board 4.

After the sample detectors were assembled, they were tested in the samemanner as was done for embodiment 1. The average sensitivity of thesample was found to be 112 mVp-p.

As can be plainly seen, the infrared detectors of these inventions donot require any special processes for providing electrical conductionbetween the infrared detector element and the circuit board, and theamount of heat that is lost due to heat transfer to the support for theinfrared detector element is very small. In addition, when manufacturingthe infrared detector of the second invention, the manufacture of thesupport and the assembly of the support with the circuit board can allbe done in one process.

Furthermore, it was possible to provide an infrared detector withoptimum sensitivity by greatly improving the productivity.

We claim:
 1. An infrared detector comprising an infrared detectorelement for generating an electrical signal, a support for the infrareddetector element, and a circuit board for receiving the electricalsignal from the infrared detector element, wherein the support is formedwith a matrix of composite material essentially consisting of one ofthermosetting resins and thermoplastic resins and carbon fibersdispersed in the matrix, said one of thermosetting resins andthermoplastic resins having a thermal deformation temperature of atleast 100° C. and a tensile elastic modulus of at least 100 kgf/mm²,said carbon fibers constituting in the range of 10% to 40% by weight ofthe matrix, and wherein the circuit board is formed with a through-holehaving an inner surface processed so as to be electrically conductive,and the support is formed integrally with the circuit board.
 2. Theinfrared detector of claim 1, wherein the circuit board is made from analumina material.
 3. The infrared detector of claim 1, wherein thethermosetting resin is selected from the group consisting of phenolresin, amino (urea) resin, melamine resin, unsaturated polyester, andepoxy resin.
 4. The infrared detector of claim 1, wherein thethermoplastic resin is selected from the group consisting ofpolypropylene, polystyrene, polyvinylchloride, polyacetal, polyamide(nylon), polycarbonate, polyphenylene ethyl, polyethylene terephthalate,polyarylate, polybutylene terephthalate, polysulfone, polyethersulfone,polyimide, polyamidimide, polyphenylene sulfide, polyoxybenzoyl,polyether etherketone (PEE-K), polyetherimide, liquid crystal polyesterand polyphenylene oxide.